Study by MOA of extrasolar planets in gravitational microlensing events of high magnification     

I. A. Bond  N. J. Rattenbury  J. Skuljan  F. Abe  R. J. Dodd  J. B. Hearnshaw  M. Honda  J. Jugaku  P. M. Kilmartin  A. Marles  K. Masuda  Y. Matsubara  Y. Muraki  T. Nakamura  G. Nankivell  S. Noda  C. Noguchi  K. Ohnishi  M. Reid  To. Saito  H. Sato  M. Sekiguchi  D. J. Sullivan  T. Sumi  M. Takeuti  Y. Watase  S. Wilkinson  R. Yamada  T. Yanagisawa  P. C. M. Yock 《Monthly notices of the Royal Astronomical Society》2002,333(1):71-83

A search for extrasolar planets was carried out in three gravitational microlensing events of high magnification, MACHO  98–BLG–35  , MACHO  99–LMC–2  and OGLE  00–BUL–12  . Photometry was derived from observational images by the MOA and OGLE groups using an image subtraction technique. For MACHO  98–BLG–35  , additional photometry derived from the MPS and PLANET groups was included. Planetary modelling of the three events was carried out in a supercluster computing environment. The estimated probability for explaining the data on MACHO  98–BLG–35  without a planet is <1 per cent. The best planetary model has a planet of mass ∼(0.4–1.5)× M _Earth at a projected radius of either ∼1.5 or ∼2.3 au. We show how multiplanet models can be applied to the data. We calculate exclusion regions for the three events and find that Jupiter-mass planets can be excluded with projected radii from as wide as about 30 au to as close as around 0.5 au for MACHO  98–BLG–35  and OGLE  00–BUL–12  . For MACHO  99–LMC–2  , the exclusion region extends out to around 10 au and constitutes the first limit placed on a planetary companion to an extragalactic star. We derive a particularly high peak magnification of ∼160 for OGLE  00–BUL–12  . We discuss the detectability of planets with masses as low as Mercury in this and similar events.  相似文献   

The MOA catalogue of eclipsing binary stars in the Small Magellanic Cloud     

G.Bayne  W.Tobin  J. D.Pritchard  I.Bond  K. R.Pollard  S. C.Besier  S.Noda  T.Sumi  T.Yanagisawa  M.Sekiguchi  M.Honda  Y.Muraki  M.Takeuti  J. B.Hearnshaw  P. M.Kilmartin  R. J.Dodd  D. J.Sullivan  P. C. M.Yock 《Monthly notices of the Royal Astronomical Society》2002,331(3):609-614

We present a catalogue of 167 eclipsing binary stars in the Small Magellanic Cloud (SMC) derived from the data base of time-series photometry for 400 000 SMC stars acquired by the Microlensing Observations in Astrophysics (MOA) project during 1997. We print coordinates, ephemerides, magnitudes and light curves for the 35 new detections; similar data and finding charts are available electronically for the whole catalogue. The majority of periods lie within the range 0.4 to 20 d; six systems are possibly eccentric while 14 are probably or certainly so. The majority of the newly identified systems lie in the outer regions of the SMC.  相似文献   

The discovery of a persistent quasi-periodic oscillation in the intermediate polar TX Col     

N. Mhlahlo  D. A. H. Buckley  V. S. Dhillon  S. B. Potter  B. Warner  P. Woudt  G. Bolt  J. McCormick  R. Rea  Denis J. Sullivan  F. Velhuis 《Monthly notices of the Royal Astronomical Society》2007,380(1):133-141

We report on the detection of an ∼5900 s quasi-periodic variation in the extensive photometry of TX Col spanning 12 yr. We discuss five different models to explain this period. We favour a mechanism where the quasi-periodic variation results from the beating of the Keplerian frequency of the 'blobs' orbiting in the outer accretion disc with the spin frequency and from modulated accretion of these 'blobs' taking place in a shocked region near the disc/magnetosphere boundary.  相似文献   

Deep SAURON spectral imaging of the diffuse Lyman α halo LAB1 in SSA 22     

R. G. Bower  S. L. Morris  R. Bacon  R. J. Wilman  M. Sullivan  S. Chapman  R. L. Davies  P. T. de Zeeuw  E. Emsellem 《Monthly notices of the Royal Astronomical Society》2004,351(1):63-69

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Pacific Atmospheric Sulfur Experiment (PASE): dynamics and chemistry of the south Pacific tropical trade wind regime     

Alan Bandy  Ian C. Faloona  Byron W. Blomquist  Barry J. Huebert  Antony D. Clarke  Steven G. Howell  R. L. Mauldin  Christopher A. Cantrell  James G. Hudson  Brian G. Heikes  John T. Merrill  Yuhang Wang  Daniel W. O��Sullivan  Wolfgang Nadler  Douglas D. Davis 《Journal of Atmospheric Chemistry》2011,68(1):5-25

The Pacific Atmospheric Sulfur Experiment (PASE) was a comprehensive airborne study of the chemistry and dynamics of the tropical trade wind regime (TWR) east of the island of Kiritibati (Christmas Island, 157º, 20?? W, 2º 52?? N). Christmas Island is located due south of Hawaii. Geographically it is in the northern hemisphere yet it is 6?C12º south of the intertropical convergence zone (ITCZ) which places it in the southern hemisphere meteorologically. Christmas Island trade winds in August and September are from east south east at 3?C15 ms^?1. Clouds, if present, are fair weather cumulus located in the middle layer of the TWR which is frequently labeled the buffer layer (BuL). PASE provided clear support for the idea that small particles (80 nm) were subsiding into the tropical trade wind regime (TWR) where sulfur chemistry transformed them to larger particles. Sulfur chemistry promoted the growth of some of these particles until they were large enough to activate to cloud drops. This process, promoted by sulfur chemistry, can produce a cooling effect due to the increase in cloud droplet density and changes in cloud droplet size. These increases in particle size observed in PASE promote additional cooling due to direct scattering from the aerosol. These potential impacts on the radiation balance in the TWR are enhanced by the high solar irradiance and ocean albedo of the TWR. Finally because of the large area involved there is a large factional impact on earth??s radiation budget. The TWR region near Christmas Island appears to be similar to the TWR that persists in August and September, from southwest of the Galapagos to at least Christmas Island. Transport in the TWR between the Galapagos and Christmas involves very little precipitation which could have removed the aerosol thus explaining at least in part the high concentrations of CCN (??300 at 0.5% supersaturation) observed in PASE. As expected the chemistry of sulfur in the trade winds was found to be initiated by the emission of DMS into the convective boundary layer (BL, the lowest of three layers). However, the efficiency with which this DMS is converted to SO₂ has been brought into further question by this study. This unusual result has come about as result of our using two totally different approaches for addressing this long standing question. In the first approach, based on accepted kinetic rate constants and detailed steps for the oxidation of DMS reflecting detailed laboratory studies, a DMS to SO₂ conversion efficiency of 60?C73% was determined. This range of values lies well within the uncertainties of previous studies. However, using a completely different approach, involving a budget analysis, a conversion value of 100% was estimated. The latter value, to be consistent with all other sulfur studies, requires the existence of a completely independent sulfur source which would emit into the atmosphere at a source strength approximately half that measured for DMS under tropical Pacific conditions. At this time, however, there is no credible scientific observation that identifies what this source might be. Thus, the current study has opened for future scientific investigation the major question: is there yet another major tropical marine source of sulfur? Of equal importance, then, is the related question, is our global sulfur budget significantly in error due to the existence of an unknown marine source of sulfur? Pivotal to both questions may be gaining greater insight about the intermediate DMS oxidation species, DMSO, for which rather unusual measurements have been reported in previous marine sulfur studies. The 3 pptv bromine deficit observed in PASE must be lost over the lifetime of the aerosol which is a few days. This observation suggests that the primary BrO production rate is very small. However, considering the uncertainties in these observations and the possible importance of secondary production of bromine radicals through aerosol surface reactions, to completely rule out the importance of bromine chemistry under tropical conditions at this time cannot be justified. This point has been brought into focus from prior work that even at levels of 1 pptv, the effect of BrO oxidation on DMS can still be quite significant. Thus, as in the case of DMS conversion to SO₂, future studies will be needed. In the latter case there will need to be a specific focus on halogen chemistry. Such studies clearly must involve specific measurements of radical species such as BrO.  相似文献   

Trace metal contamination of Beaufort's Dyke, North Channel, Irish Sea: a legacy of ordnance disposal     

Callaway A  Quinn R  Brown CJ  Service M  Benetti S 《Marine pollution bulletin》2011,62(11):2345-2355

Beaufort’s Dyke is a disused ordnance disposal ground within the North Channel of the Irish Sea. Over 1 million tonnes of ordnance were disposed of in the dyke over a 40 year period representing a substantial volume of trace metal pollutants introduced to the seabed. Utilising particle transport modelling software we simulated the potential transport of metal particles from Beaufort’s Dyke over a 3 month period. This demonstrated that Beaufort’s Dyke has the potential to act as a source for trace metal contamination to areas beyond the submarine valley. Trace metal analysis of sediments from the Dyke and surrounding National Marine Monitoring Programme areas demonstrate that the Dyke is not the most contaminated site in the region. Particle transport modelling enables the transport pathways of trace metal contaminants to be predicted. Implementation of the technique in other munitions disposal grounds will provide valuable information for the selection of monitoring stations.  相似文献   

Quantifying water vulnerability: a multi-dimensional approach   总被引：2，自引：0，他引：2  

Caroline A. Sullivan 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):627-640

In today’s uncertain world, vulnerability of water supplies is of increasing concern. A number of factors influence this, ranging from physical conditions through to human management capacities. Across the Orange River Basin in southern Africa, these threats arise from overpopulation and farming pressure, with agrochemical and industrial runoff as well as harsh weather conditions giving rise to severe problems of erosion and land degradation. Under conditions of climate change, these threats are exacerbated, as temperature rises and water resources become more erratic. Since water is both an essential instrument of livelihood support and a crucial factor of production, there is a need to develop more effective mechanisms to identify those areas where its scarcity or poor management can bring about a slowdown in the development process. This urgency is heightened by the international commitment to the Millennium Development Goals (MDGs), supposedly to be reached by 2015. In addition to the MDGs, governments are also committed to the development of basin management plans for Integrated Water Resources Management (IWRM). This means that, in order to try to allocate water in an equitable and efficient way, better understanding is needed of all of the complexities of managing water across heterogeneous basins. It is now recognized that effective water management is much more dependent on effective governance than on hydrologic regimes. Ranging from traditional local customary norms and practices dating back through generations to the latest state-of-the-art science-based international agreements, water governance is a key to supporting the lives and livelihoods of local populations. Access to information is an essential feature of any of these approaches, and harmonization of data on water issues is long overdue. This paper provides an outline of an index-based methodology on which an assessment of water vulnerability can be made. In this approach, supply-driven vulnerability (from water systems) and the demand-driven vulnerability (from water users), are evaluated at the municipal scale. By combining these various dimensions together mathematically, a Water Vulnerability Index (WVI) can be generated.  相似文献   

Structural geology of the Upper Cretaceous Chalk Central Mass, Isle of Wight, U.K.     

Rory Mortimore 《Proceedings of the Geologists' Association. Geologists' Association》2011,122(2):298-331

Remapping the Chalk of the Central Chalk Mass of the Isle of Wight between Carisbrooke (Newport), Calbourne and Shalcombe, including the Bowcombe Valley, has identified a complex series of tectonic ‘rolls’ and ‘flats’ in a region that has been interpreted to be a relay ramp between the Needles and the Sandown faults. A major new WNW trending fault at Cheverton throws the Chalk down by >50 m to the SW in a 80-100 m wide zone of faulting within which some chalk blocks have near vertical dips. The fault location and trend closely follows the edge of the Cranbourne-Fordingbridge High and could also reflect, for the first time, the surface expression of part of the Needles Fault, a major inversion reverse fault. Located along this fault zone deep Quaternary weathering of the Chalk and Quaternary gravel deposits are present. The trend of the Cheverton Fault brings it towards Gotten Leaze where a groundwater pumping station is located and groundwater springs regularly cause flooding on the Brighstone-Calbourne Road. Analyses of the jointing in the Chalk show that stratabound fracture patterns typical of the Chalk formations elsewhere in Southern England are present in the Central Mass. In addition, there are numerous small faults along which valleys have formed. Tectonic structure and lithology have had a profound influence on the geomorphology and groundwater flow in the Chalk in the Central Mass.  相似文献   

Iron geochemical zonation in a tidally inundated acid sulfate soil wetland     

Scott G. Johnston  Annabelle F. Keene  Richard T. Bush  Edward D. Burton  Leigh A. Sullivan  Lloyd Isaacson  Angus E. McElnea  Col R. Ahern  C. Douglas Smith  Bernard Powell 《Chemical Geology》2011,280(3-4):257-270

Tidal inundation is a new technique for remediating coastal acid sulfate soils (CASS). Here, we examine the effects of this technique on the geochemical zonation and cycling of Fe across a tidally inundated CASS toposequence, by investigating toposequence hydrology, in situ porewater geochemistry, solid-phase Fe fractions and Fe mineralogy. Interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation, redistribution and subsequent mineralogical transformations of Fe within the landscape. Reductive dissolution of Fe(III) minerals, including jarosite (KFe₃(SO₄)₂(OH)₆), resulted in elevated concentrations of porewater Fe²⁺ (> 30 mmol L^?1) in former sulfuric horizons in the upper-intertidal zone. Tidal forcing generated oscillating hydraulic gradients, driving upward advection of this Fe²⁺-enriched porewater along the intertidal slope. Subsequent oxidation of Fe²⁺ led to substantial accumulation of reactive Fe(III) fractions (up to 8000 μmol g^?1) in redox-interfacial, tidal zone sediments. These Fe(III)-precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation. Schwertmannite (Fe₈O₈(OH)₆SO₄) was the dominant Fe mineral phase in the upper-intertidal zone at mainly low pH (3–4). This was followed by increasing lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) at circumneutral pH within lower-intertidal and subtidal zones. Relationships were evident between Fe fractions and topography. There was increasing precipitation of Fe-sulfide minerals and non-sulfidic solid-phase Fe(II) in the lower intertidal and subtidal zones. Precipitation of Fe-sulfide minerals was spatially co-incident with decreases in porewater Fe²⁺. A conceptual model is presented to explain the observed landscape-scale patterns of Fe mineralisation and hydro-geochemical zonation. This study provides valuable insights into the hydro-geochemical processes caused by saline tidal inundation of low lying CASS landscapes, regardless of whether inundation is an intentional strategy or due to sea-level rise.  相似文献   

A new, large tyrannosaurine theropod from the Upper Cretaceous of China   总被引：2，自引：0，他引：2  

David W.E. Hone  Kebai WangCorwin Sullivan  Xijin ZhaoShuqing Chen  Dunjin LiShuan Ji  Qiang JiXing Xu 《Cretaceous Research》2011,32(4):495-503

Tyrannosaurids are primarily gigantic, predatory theropod dinosaurs of the Cretaceous. Here we report a new member of the tyrannosaurid clade Tyrannosaurinae from the Upper Cretaceous Wangshi Group of Zhucheng, Shandong Province, China, based on a maxilla and associated dentary. The discovery of this animal, here named Zhuchengtyrannus magnus gen. et sp. nov., adds to the known diversity of tyrannosaurids in Asia. Z. magnus can be identified by a horizontal shelf on the lateral surface of the base of the ascending process, and a rounded notch in the anterior margin of the maxillary fenestra. Several additional features contribute to a unique combination of character states that serves to further distinguish Z. magnus from other taxa. Comparisons with other tyrannosaurids suggest that Zhuchengtyrannus was a very large theropod, comparable in size to both Tarbosaurus and Tyrannosaurus.  相似文献